The present invention relates to intraocular lenses (IOLs). More particularly, the invention relates to IOLs including surrounded lens zones which are adapted to provide accommodation in the eye.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens, a ciliary muscle, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Recently, multifocal IOLs without accommodating movement have been used to provide near/far vision correction.
Attempts have been made to provide IOLs with accommodating movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691 and several patents to Cumming, including U.S. Pat. Nos. 5,674,282 and 5,496,366. The disclosure of each of these patents is incorporated herein by reference. One problem that exists with such IOLs is that they often cannot move sufficiently to obtain the desired accommodation.
It would be advantageous to provide IOLs adapted for accommodating movement which can achieve an increased amount of accommodation.
New accommodating IOLs have been discovered. The present accommodating IOLs take advantage of employing an optic made of two different materials to enhance the accommodation achievable in the eye in response to normal accommodative stimuli. Thus, the present lenses provide for controlled vision correction or focusing for both near objects and far or distant objects. Further, a greater overall range of accommodation is often achieved. The present IOLs are relatively straightforward in construction and to manufacture or produce, can be implanted or inserted into the eye using systems and procedures which are well known in the art and function effectively with little or no additional treatments or medications being required.
In one broad aspect of the present invention, intraocular lenses (IOLs) are provided and comprise an optic adapted to focus light toward a retina of a mammalian eye and, in cooperation with the mammalian eye, to provide accommodation. The optic includes a first lens portion adapted to move in response to the action of the mammalian eye; and a second lens portion surrounded by the first lens portion of the optic, and having a higher refractive index or index of refraction than the first portion and/or being less deformable than the first portion in response to forces exerted by the mammalian eye.
The first lens portion is comprised of an optically clear material that is easily reshaped and/or is axially movable when exposed to force exerted by the mammalian eye. The second lens portion of the optic is comprised of an optically clear material having a higher refractive index than the first portion and/or being less deformable than the mammalian eye. For example, the first lens portion may have a refractive index of about 1.37 or less, while the second portion preferably has a refractive index of at least about 1.42. The difference in refractive index between the first and second portions may be in the range of at least about 0.03 and may be in the range of about 0.04 to about 0.1 or more. However, the second portion of the present optic may have a higher, lower or the same refractive index relative to the refractive index of the first portion. For example, both first and second portions of the present optics may have refractive indexes of about 1.37 or less. In one useful embodiment, both the first and second lens portions have refractive indexes of at least about 1.40 and/or at least about 1.42.
The second lens portion may be deformable or reshapable by the force exerted on the optic by the eye or may be substantially rigid in response to such force. As a result of this, potential materials for the second lens portion may vary significantly.
In one embodiment, the present lenses very effectively provide for both enhanced movement, for example reshaping and/or axial movement because of the substantially compliant or deformable first lens portion, while, at the same time, providing effective corrective optical powers with a reduced sized, e.g., thickness, lens because of the higher refractive index second lens portion. This combination of enhanced movement and high refractive index provides a substantial benefit in achieving accommodation in the mammalian eye.
Advantageously, the second lens portion of the optic is less deformable in the eye than is the first lens portion. Having a second portion with reduced deformability adds stability to the optic in the eye. The movement, for example, reshaping and/or axial movement, of the optic in the eye is achieved with reduced risk that such movement can misshape or otherwise distort the optic which can detrimentally affect the vision of the wearer of the IOL. In other words, the relatively rigid second lens portion of the optic may provide for a more controlled or reproducible movement of the optic in the eye relative to a similar optic without the second portion.
The second lens portion of the optic may be positioned at any suitable location in the optic. The second portion advantageously is substantially symmetrical about the optical axis of the optic. The second portion preferably is substantially centrally located within the first portion. The second lens portion is often secured to the first lens portion.
In one very useful embodiment, the first lens portion of the optic is adapted to be reshaped in response to the action of the mammalian eye. In particular, the first lens portion includes an anterior surface and is adapted to be reshaped in response to the action of the mammalian eye. This reshaping preferably is effective to change the curvature of the first portion, for example, the anterior surface of the first portion. Such change in curvature alters the optical power of the optic and is effective in providing at least a portion of the desired accommodation. Alternately, and preferably in conjunction with the reshaping of the first lens portion, this first portion may be adapted to move axially in the mammalian eye in response to the action of the mammalian eye to provide additional accommodation.
Advantageously, the first and second lens portions of the optic are located so that their central axes are aligned with the optical axis of the optic. Looked at from another perspective, the second lens portion may be considered as a core or center of the optic while the first portion may be considered an outer layer or covering of the optic.
The reshaping or deformation of the first portion can cause an axial movement of the first portion which imparts an axial movement of the second portion of the optic. Axial movement of the portion of the optic with the greater dioptic power, most likely the high refractive index portion, e.g., the second lens portion, of the optic, has a relatively large effect on the accommodative power of the optic. Thus, axial movement of the second portion of the optic can be one feature of the present invention effective in providing accommodation. Of course, reshaping of the first portion in and of itself provides accommodative power, for example, by changing the curvature of the anterior surface of the first portion. The overall accommodative power of the optic in accordance with the present invention preferably is increased beyond the simple axial movement of a single lens of uniform composition, for example, because of the reshaping or deformation of the first lens portion.
In another very useful embodiment, a force transfer assembly is provided. This force transfer assembly has a first end coupled to the optic and a second end extending away from the optic and adapted to contact a posterior bag of the mammalian eye when the IOL is located in the mammalian eye. The force transfer assembly is adapted to transfer the force exerted by the eye to the optic to facilitate the movement of the optic. Preferably, the force transfer assembly is adapted to transfer the force exerted by the eye to the optic to facilitate at least one of reshaping the first portion in response to the action of the mammalian eye and moving the first portion axially in the mammalian eye in response to the action of the mammalian eye. In a very useful embodiment, the force transfer assembly is adapted to transfer force from the eye to the optic to facilitate reshaping of the optic or reshaping of the optic and moving the optic axially in the eye. The force transfer assembly is very effective in facilitating the accommodation obtained by the present IOLs.
However, it should be noted that such force transfer assembly is not essential in accordance with the present invention. The optic can be sized and configured to fit within the capsular bag and to contact the capsular bag, in particular the periphery of the capsular bag, so that the force exerted by the eye can be transferred directly to the optic of the present IOL. Such IOLs in which the optics are sized and configured to contact the peripheral capsular bag are very effective in being reshaped to provide the desired accommodation. In addition, substantially filling the capsular bag volume with a deformable optic including a first lens portion and a second lens portion, as in the present optics, reduces the risk of decentration or tilt of the lens system in the eye, as well as reducing the risk of decentration or tilt between individual lens components, relative to lens systems in which the optic does not substantially fill the capsular bag volume. Providing for a reduced risk of decentration is highly advantageous, for example, as the capsular bag contracts. Even if the contraction of the capsular bag is asymmetric, for example, because the zonules are not of uniform strength, the elastic properties of the first portion mitigate against this asymmetry and reduce the risk of decentration.
Substantially filling the capsular bag volume, as described above, may reduce the risk of posterior capsular opacification (PCO) particularly if the posterior surface of the optic remains in contact with the posterior wall of the capsular bag during all states of accommodation.
In a very useful embodiment, the present IOLs are deformable for insertion into the mammalian eye through a relatively small incision, for example on the order of about 3.5 mm or less. Thus, both the first and second lens portions of the optic, and the force transfer assembly, if present, are all deformable for insertion through a small incision into the eye. Such IOLs regain their original undeformed condition rapidly after being inserted into the mammalian eye.
In order to facilitate the movement in the eye, the first portion preferably is more deformable than the second portion of the present IOLs. As noted previously, the second portion can be substantially rigid, for example, in response to forces exerted in the eye. However, it is preferred that the entire IOL be sufficiently deformable to be passed through an incision in the eye which is less than the diameter of the IOL in its undeformed condition.
The present optics may be made of any suitable materials of construction. For example, the present optics may be made of one or more polymeric materials employing techniques used in manufacturing conventional polymeric material IOLs. Examples of the materials from which the present optics can be made include, without limitation, acrylic polymeric materials, silicone polymeric materials, and the like and combinations thereof. Although combinations of different polymeric materials may be employed, the present optics preferably are made of different polymeric materials of the same general chemical family. For example, the first lens portion of the IOL may be made of one silicone polymeric material while the second portion is made of a different silicone polymeric material. Similarly, the first portion of the optic can be made of one acrylic polymeric material while the second lens portion is made of a different acrylic polymeric material. In any event, the first portion of the present optics and the second portion and third portion, if present, preferably are made of compatible materials of construction, that is materials which can be used to produce an effective IOL which remains as an intact structure in the eye without significant deterioration for periods of time extending for at least about 20 or about 25 years or more.
In one embodiment, the first lens portion of the present optics is made of a very low modulus silicone polymeric material, while the second portion is made of a higher refractive index silicone. To illustrate, the first portion of the optic can be composed of a silicone polymeric elastomer with the following material properties:
Optically clear;
Refractive index of at least about 1.37;
Shore A hardness of about 0; and
At least about 1000% elastic elongation.
The second lens portion of the present optics can be made of a different silicone elastomer with the following material properties:
Optically clear;
Refractive index of about 1.42 or higher;
Shore A hardness in a range of about 0 to about 30; and
An elastic elongation higher than about 150%, preferably in a range of about 150% to about 400%.
The second lens portion can be made of widely varying materials. Examples include, without limitation, rigid and foldable acrylic polymeric materials, rigid and foldable non-acrylic polymeric materials, deformable or foldable silicone polymeric materials and the like and combinations thereof. The second portion can be hydrophobic or hydrophilic.
Many materials which meet the above-noted criteria are conventional and well known in the art. Therefore, a detailed description of such compositions is not presented here.
However, by way of illustration, the following materials of construction, based on constituent monomeric components, is presented.
The present optics are conveniently produced using conventional and well known techniques, such as molding techniques. In one embodiment, the second portion is produced in a separate mold and then inserted into a mold into which is placed the monomeric or partially polymerized monomeric mixture of the first portion precursors. The combination is then heated to elevated temperatures, for example on the order of about 40xc2x0 C. to about 100xc2x0 C., and/or subjected to ultraviolet radiation and the composition combination is allowed to cure, preferably for about one hour to about 24 hours. The material in the mold is then post-cured, preferably at a temperature in the range of about 70xc2x0 C. to about 130xc2x0 C., and/or being subjected to ultraviolet radiation for a period of time, preferably for about two hours to about 30 hours. After curing (and post-curing), the mold is disassembled and the molded lens body recovered.
The force transfer assembly, if present, can be made or provided separately and then coupled to the optic or lens body, for example, in a mold in which the optic is cured or post-cured. Alternately, the force transfer assembly can be coupled to the lens body after the lens body is formed. Conventional techniques can be employed. For example, one or more recesses can be formed in the optic and the force transfer assembly can be secured to the optic by having an end placed in the recess, for example, in much the same manner in which a haptic or fixation member is secured to the optic of a conventional IOL.
Any suitable material or combination of materials of construction may be utilized in the force transfer assembly and the force transfer assembly can have any suitable configuration provided that such assembly is effective to at least partially transfer the force of the eye to the optic of the IOL. The force transfer assembly preferably is more rigid or less flexible than the first portion of the optic. However, the force transfer assembly preferably is sufficiently deformable to be folded or otherwise deformed to pass through a small incision for insertion into the eye. The force transfer assembly can be a single member substantially surrounding the optic, or can be a plurality, for example, about 2 or about 3 to about 4 or about 6, individual elements positioned around the peripheral edge of the optic. Although the force transfer assembly can include at least one hinge to facilitate axial movement of the optic in response to the action of the eye, preferably the force transfer assembly does not include a hinge.
The force transfer assembly preferably is made of a material or materials which are compatible with the eye and with the other material or materials included in the IOL. Examples of materials which can be included in the present force transfer assemblies include, but are not limited to, polypropylene, silicone polymeric materials, acrylic polymeric materials including but not limited to polymethylmethacrylate (PMMA), polyamides and the like and combinations thereof.
In a further broad aspect of the present invention, methods for inserting an IOL in an eye are provided. Such methods comprise providing an IOL in accordance with the present invention, as described herein. The IOL is placed into the eye, for example in the capsular bag of the eye, using equipment and techniques which are conventional and well known in the art. The IOL is placed in the eye so that the eye effectively cooperates with the IOL to provide accommodation as desired. After the IOL is inserted into the eye, any incision in the eye is closed. After a relatively short period of recuperation, the IOL provides the wearer of the IOL with substantially effective accommodation. No further treatments or medications, for example, to paralyze the ciliary muscle, to facilitate fibrosis or otherwise influence the position of the IOL in the eye, are required. Preferably the optic is deformed prior to being placed into the eye. Once the IOL is placed in the eye, and after a normal period of recovery from the surgical procedure, the IOL, in cooperation with the eye, provides the mammal or human wearing the IOL with the desired accommodation.
Any and all features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combinations are not mutually inconsistent.
Additional aspects and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.